The research program will be concerned with production, function, and regulation of histone messenger RNA and the histones themselves in sea urchin embryos and in cell populations cultured from separated blastomeres of the sixteen-cell stage. As methods are evolved for them with similar specificity, the maternal messenger RNAs that encode other proteins synthesized during development will be studied according to the same general protocols. Maternal mRNA, isolated initially as ribonucleoprotein particles sedimenting at 20S - 60S, will be purified from unfertilized eggs, from separated blastomeres of the sixteen cell stage, and from cultures of these blastomeres maintained under various conditions of allowed cell-cell interaction. The RNP particles themselves or their constituent mRNAs will be translated in cell-free systems capable of synthesizing normal proteins on eukaryotic mRNA. Multidimensional separation of product polypeptides will be used to determine the extent to which cleavage blastomeres inherit different populations of maternal mRNA. The latter will be selected, as against newly-transcribed ones, by culture of the embryos and derived cell lineages in Actinomycin D. Long-term objectives, other than those directed specifically toward understanding the changing histone content of chromatin as development proceeds, concern a test of the hypothesis that maternally or oogenetically-transcribed mRNA and other informational RNAs are a physical basis of asymmetric morphogenetic potential in the zygote.